1. Field of the Invention
The present invention relates generally to telecommunications and, more particularly, to managing supplemental channel data rates in a wireless telephone system.
2. Description of the Related Art
This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present invention, which are described and claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present invention. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
One of the paramount challenges facing modern wireless telephone systems is the rapid growth of consumer demand for data services such as Internet access, text messaging, and e-mail. In fact, consumers are demanding greater access to data-related services than ever before, and this trend is not likely to change. For example, in the coming years, consumers will likely expect their wireless telephones to provide many, if not all, of the communication features currently provided by computers (e.g., video conferencing, picture mail, etc.).
Unfortunately, building or upgrading the telecommunication infrastructure to support growing consumer demand is relatively expensive. As such, much research has been invested into determining better and more efficient methods for transmitting information over existing infrastructure. Early designs used multiple frequencies to simultaneously transmit multiple signals in parallel. This technology worked well with a small number of users, but as the number of user grew, there were simply not enough frequencies for each user. Code Division Multiple Access (“CDMA”) is one technique that addresses this problem. In a CDMA system, wireless telephone calls are no longer divided by frequency. Rather all wireless telephone calls are transmitted at the same time and at the same frequency. While this technique may appear chaotic, each individual telephone or mobile device is able to recognize its call by a unique code assigned to that call. This unique code allows many users to share a single frequency.
Modern wireless telephone systems, such as CDMA 2000 3G-1X, CDMA 2000 1X EV-DV, CDMA 2000 3X, and WCDMA UMTS, provide at least two types of channels to transmit telephone calls or other data from a wireless telephone base station to a wireless device and vice versa. The first of these channels is known as the fundamental channel (“FCH”). Every wireless device in communication with a base station is assigned an FCH, which is typically configured to transmit at 9.6 kilobits per second (“Kb/s”). Due to the relatively low data rate of the FCH, FCHs are typically employed to transmit only voice data (i.e., telephone conversations), because voice data uses a relatively low and substantially stable data rate.
A second type of channel employed in modern wireless telephone systems is known as a supplemental channel (“SCH”). The SCH allows data rates of up to 307.2 Kb/s, and each mobile device can be allocated up to two SCHs at a time. Unlike the FCH, however, every wireless device in communication with a base station is not typically assigned an SCH. Rather, the base station temporarily establishes an SCH at a particular data rate when the base station has additional data to transmit to a particular wireless device. For example, if a user wishes to download a large picture from the Internet, the base station may assign the user's mobile device an SCH with a data rate of 300 Kb/s, for example, to use until the picture is downloaded. If, however, the user wishes to download a smaller text file, the base station may assign the user's mobile device an SCH with a data rate of 50 Kb/s, for example.
There are several factors, however, that complicate the assignment of SCHs in a wireless telephone system. First, is the allocation of transmission power. Transmission power is one of the base stations most important commodities, because there is a limited amount of transmission power available in a wireless telephone system. A portion of this transmission power is allocated to maintaining a constant data rate of 9.6 Kb/s for the FCH of every mobile device and for maintaining overhead channels (e.g., pilot, paging, and sync channels). The power that remains after the base station has allocated power to these channels can be allocated to the SCHs.
By increasing transmission power to a wireless device, the base station can improve the signal quality, the signal distance, the signal penetration, and/or the signal data rate. For example, it takes more power to transmit a signal to a mobile device that is relatively distant from the base station or to transmit a signal to a mobile device that is inside a building. Similarly, all other things being equal, it takes more transmission power to transmit a 300 Kb/s signal than a 50 Kb/s signal. As such, allocating data rates for SCHs amongst the users of the wireless telephone system can create conflicts amongst users. For example, establishing a 50 Kb/s supplemental channel with a user inside a building that is relatively far from the base station may use the same amount of transmission power as three 300 Kb/s SCHs for wireless devices relatively close (e.g., within a direct line of site) to the base station. As such, one of the challenges in allocating base station power is managing data rates for all of the users to most fairly or appropriately use the available transmission power.
Second, wireless telephone providers are interested in allocating bandwidth and throughput based on the Quality of Service (“QoS”) parameters for each mobile devices. QoS enables differentiation between different types of applications or services on the wireless telephone network. To improve efficiency, modern wireless telephone systems may attempt to allocate data rates based on the QoS parameters for each particular application or service. For example, voice services may be assigned a lower data rate than web services. The particular QoS parameters may be determined by the operators of the wireless telephone service and may vary greatly depending on the particular service provided. Accordingly, efficiently managing the data rates to each of the mobile devices based on QoS parameters may also be beneficial.
Third, with rapid growth of data-based services, such as wireless Internet, wireless telephone providers may also be concerned with the Grade of Service (“GoS”). GoS enables differentiation between different classes of users. A wireless telephone provider may sell different services packages, referred to as GoS classes, at different prices. For example, a more expensive access package may provide higher data rates, while a less expensive access plan may provide only lower data rates. A system that can provide a variety of price/performance packages may be commercially advantageous to wireless telephone service providers.
Fourth, modern wireless telephone systems may also take into account fairness in assigning data rates. In an ideal system, it would be possible to satisfy the requirements of every mobile device of every user instantaneously. However, for a variety of reasons (such as those discussed above), this is generally not currently feasible. As such, some users may encounter delays or errors. Fairness concerns are directed towards insuring that these errors or delays are fairly apportioned amongst all of the users of the wireless telephone system depending on QoS parameters and GoS class, if applicable. For example, in a system employing an “equal throughput” fairness scheme, the wireless telephone system attempts to ensure that every user has equal data rates over time subject to QoS parameters and GoS class. Whereas, in a “proportional throughput” fairness scheme, the wireless telephone system attempts to ensure that every user has equal access to transmission power subject to QoS parameters and GoS class. As such, in a proportional throughput system, users farther away from the base station may be assigned lower data rates than closer users because, as described above, it takes more transmission power to transmit to mobile devices that are farther away.
A system that could manage the allocation of supplemental channel data rates in a wireless telephone system based on the factors outlined above would be advantageous.